1. Field of the Invention
The present invention relates generally to apparatus and methods for separating cellular material from biological fluids and, more particularly, to the design and use of a centrifugal rotor which is capable of separating plasma from a measured volume of whole blood and optionally distributing the plasma to a plurality of test wells within the rotor.
Blood tests frequently require that potentially-interfering cellular components of the blood be separated from the blood plasma prior to testing of the plasma. It is also frequently desirable to divide the separated blood plasma into a plurality of discrete aliquots so that a variety of tests or assays may be performed on the blood. Such separation and division steps have heretofore been typically performed by centrifugation to separate the blood plasma from the cellular components, followed by manual or automated pipetting of the blood plasma into separate test wells. Such procedures are labor intensive and time-consuming, and various automated systems and methods have been proposed for providing multiple aliquots of plasma suitable for testing in a more efficient manner.
Of particular interest to the present invention are centrifugal rotors which have been modified both to separate plasma from whole blood and to distribute the separated plasma into separate test wells. The use of such rotors can provide a plurality of discrete plasma volumes which may be tested or evaluated, all present within the centrifugal rotor, greatly enhancing the efficiency of automated testing procedures.
Although a significant improvement over prior manual or partly manual procedures, previous modified centrifugal rotors have suffered from a number of deficiencies. Such rotors have frequently required the application of relatively large volumes of whole blood in order to achieve the desired separation and distribution. Moreover, such rotors have frequently utilized complex designs which are difficult and costly to manufacture. Often, the rotors require various separable parts or components which are brought together or separated at different points in the centrifugation procedure. Previous centrifugal rotors have often required the user to manually measure a volume of sample prior to applying the sample to the rotor. The need to manually measure the sample volume can significantly decrease the efficiency of an otherwise automated process.
For these reasons, it would be desirable to provide improved centrifugal rotors and methods suitable for separating blood into plasma and cellular components and for further distributing the separated plasma into a plurality of discrete test wells within the rotors. The rotors and methods should be capable of metering precise quantities of blood without requiring the user to premeasure the volume being applied to the rotor. The rotor design should be simple and amenable to low-cost manufacturing procedures, and it would be further desirable if the rotors were of unitary construction with no separable or movable parts.
2. Description of the Background Art
U.S. Pat. No. 4,284,602 describes a centrifugal rotor which measures a predetermined amount of fluid by filling a measuring chamber with fluid under centrifugal force to a certain level, wherein an overflow passage allows excess fluid to flow to an outlet. U.S. Pat. No. 4,876,203 describes a centrifugal rotor which measures a predetermined quantity of fluid by filling a calibrated cell through a capillary duct from a storage chamber, the excess fluid flowing from the calibrated cell through a second capillary duct to an overflow chamber. U.S Pat. No. 3,901,658 describes a centrifugal rotor which measures predetermined volumes of blood by filling a plurality of measuring chambers with blood under centrifugal force, the excess blood flowing into an overflow passageway when a certain centripetal level is reached. U.S. Pat. No. 3,899,296 describes a centrifugal rotor which measures a discrete volume of blood by filling a passageway with blood under centrifugal force, wherein excess blood flows into an overflow chamber, and a ball check is used to seal off the inlet of the passageway after it has been filled. Other centrifugal rotors are described in U.S. Pat. Nos. 3,864,089, 3,873,217, 4,035,156, 4,225,558, 4,279,862 and 4,689,203.